标题： 等效原理和电磁场：无双折射，无稀疏子，无轴子 显示英文标题

标题： Equivalence principle and electromagnetic field: no birefringence, no dilaton, and no axion

摘要： 电磁场与引力的耦合被讨论。 在基于实验上已确立的电荷和磁通量守恒定律的非度规公理化方法中，麦克斯韦方程在有无引力的情况下都是相同的。 从这个意义上说，可以认为电荷“基底”和磁通“基底”不会直接受到引力场的影响。 然而，这些基本基底之间的相互关系，作为电磁激励H和电磁场强度F的2-形式之间的{\it 空间时间关系} H=H(F)，会受到引力的影响。 因此，电磁学中的等效原理的有效性取决于时空关系的形式。 我们讨论了非局部和局部的线性本构关系，并证明时空度规也可以伴随旋子、标量子和轴子场。 所有这些度规的非度规伙伴最终可能导致等效原理的破坏。 显示英文摘要

摘要： The coupling of the electromagnetic field to gravity is discussed. In the premetric axiomatic approach based on the experimentally well established conservation laws of electric charge and magnetic flux, the Maxwell equations are the same irrespective of the presence or absence of gravity. In this sense, one can say that the charge "substratum" and the flux "substratum" are not influenced by the gravitational field directly. However, the interrelation between these fundamental substrata, formalized as the {\it spacetime relation} H=H(F) between the 2-forms of the electromagnetic excitation H and the electromagnetic field strength F, is affected by gravity. Thus the validity of the equivalence principle for electromagnetism depends on the form of the spacetime relation. We discuss the nonlocal and local linear constitutive relations and demonstrate that the spacetime metric can be accompanied also by skewon, dilaton, and axion fields. All these premetric companions of the metric may eventually lead to a violation of the equivalence principle.